1. Field of Invention
This invention relates to innovative retrofit connectors that permanently connect and strengthen intersecting structural members on a building. These connectors help create buildings that are stronger and more resistant to earthquakes and wind storms.
During an earthquake, the floor, wall, and roof diaphragms undergo shearing and bending. Because of the difference in weight, a roof can move at different speeds than the walls. The outside sheathing provides lateral stability to the walls, preventing racking. The sheathing also helps absorb and transfer seismic forces to the piers and foundation, and then back into the ground.
An earthquake can send motion into a house and separate structural members that are nailed together. The October, 2006 earthquake on the Big Island of Hawaii shook many homes off their piers. Because there is no frost, the foundations are shallow. Almost all the homes are made of wood construction. Many homes were damaged, which was unexpected because wood homes can usually absorb seismic forces.
Because of the active and ancient volcanoes making up the Hawaiian Islands, many homes in Hawaii are built on a slope. The rear of the house can be on the ground, with the front of the home 20 or more feet off the ground. The front of the house is usually on posts or stilts made from wooden beams.
Cross-bracing ties these tall posts together. The weak point is where the 2×4 cross-braces are connected to the posts. This invention helps strengthen the braces, and helps prevent the posts from moving off their piers, thus helping prevent the home from falling during earth movements.
Steel connectors, between different components of a wood-frame building's super-structure, provide continuity so that the building will move as a unit in response to seismic activity. This invention ties the homes sub-structure securely together, so the house will move as one unit.
Recent studies of hurricane damage on wood-frame buildings indicate that extensive damage was generated to a house by strong winds, when the building moved away from the foundation, and adjacent walls moved away from each other. Failure of the elevated part of a Hawaiian home is common during hurricanes, because wind can get underneath and lift one or several structural members of the home. This invention helps prevent the posts from detaching from other structural members.
Many homes that are built in temperate climates are situated on posts, such as in California where many homes are elevated on short posts called cripples. Many of these cripples are not tied together, just covered by lattice, but could be reinforced with the present invention.
The shear forces from the roof boundary members are transferred to the top of the walls and they travel down to the floor, to the posts, and to ground. The weakest connection is usually the one that fails. To withstand and transfer the shear loads, the connection between the floor and foundation must be strong.
The cross-bracing provides lateral stability to the posts, preventing racking. The cross bracing also absorbs and transfers earthquake forces to the foundation. Unique steel connectors help strengthen and stabilize the cross-braces, and many other intersecting structural members.
2. Prior Art
Prior art connectors utilizing angled nailing were only concerned with three areas: (1) prevention of wood splitting due to wood shrinkage, (2) prevention of splitting of laminated wood members such as plywood glued laminated timbers (glulam and prefabricated wood joists (microlams), and (3) insertion of fasteners through a held member and a holding member which are joined by a special connector so that a plurality of fasteners will be in double shear. The first two problem areas are fully discussed in Gilb U.S. Pat. No. 4,291,996 Sep. 29, 1981, and the third problem area is discussed in Gilb and Commins U.S. Pat. No. 4,480,941 granted Nov. 6, 1984. These were also discussed in Leek, et al. U.S. Pat. No. 5,603,580 granted Feb. 18, 1997.
Gilb's 966′ taught the use of a slot-like opening in the face of the metal connector and then bending out a tab-like member formed from the displaced material. The tab-like device has been commercially successful with thousands of hangers carrying the positive angle nailing device.
But the tab-like device has several problems as set forth as follows: (1) the punching of a slot has a similar effect of punching a large opening in the metal which tends to weaken the metal; (2) the tab protruding from the metal tends to snag on other building materials prior to installation; (3) the protruding tab has invited installers who are not familiar with the purpose of the tab to forcibly bend the tab with a hammer or pair of pliers, thereby destroying the purpose of the tab; the tab is relatively easily bent during non-aligned hammering of the fastener during installation and (5) while the cost of forming the tab is minimal, yet it does require two stations; viz, a cutting station and a bending station thereby adding to the cost of manufacture.
Gilb and Commins 941' uses angled nailing on a connector that wraps on two sides of a wood member, like a joist hanger. Angled nailing from opposite sides of the wood member cross each other forming double-shear nailing. This basically means that a force pulling on one direction pulls the opposite nail deeper into the wood. This only works on a connector that wraps on two sides of a wood member, or in the present invention, when two connectors are used on opposite sides.
Leek's 580' uses a nail hole-sized, dome-shaped opening to angle the nail into the wood member. The dome-shape does not snag, and does not make a bigger hole in the metal connector than the nail hole itself. But it still makes a hole in the material and protrudes.
Up until this invention, the only method of making angled nailing was angling the nail hole. It was done by cutouts or by doming. No one had thought about angling the face of the connector, or if they did, how to do it properly.
There are a few connectors made for connecting sloped structural members. The Simpson Strong Tie Company catalog shows several connectors that are bent at the building site by a contractor. Their Adjustable Light Slopable Hanger (LSU), and Jack Truss Connector (TJC37) are bent in the field along a centerline of slots. Both are not patented.
The Simpson Strong Tie Company catalog shows three patented connectors for sloped structural members. Like Simpson's above connectors, all these connectors are field-bent to the desired angle. Field bending of a clip to fit on sloped structural members is described in Gibb, U.S. Pat. No. 4,410,294 granted Aug. 9, 1994; Callies, U.S. Pat. No. 5,230,198 granted Jul. 27, 1993; and Horne, U.S. Pat. No. 6,772,570 granted Aug. 10, 2004.
3. Objects and Advantages
Accordingly, several objects and advantages of my invention are that it helps secure intersecting structural members of a building to make the building a solid unit and helping prevent it from being destroyed by hurricanes and earthquakes.
One advantage is this invention doesn't split the wood, because the nail is driven away from the edge of the wood. When the invention is installed, it helps hold the edge of the wood together.
Another advantage is that the driven nail is at an acute angle into the heart of the wood member. A nail driven perpendicular near the edge of a flush face is more prone to forces that can pull straight on the nail. But an angled nail must usually be sheared, as it's difficult to pull it out from the heart of the wood at an angle. Wind or seismic events usually create forces that try to pull structural members straight apart.
Still another advantage is that this invention can use a longer nail in the wood. A 2×4 is actually 1½ inches thick. This invention puts the nail at an angle into the heart of the wood. That means that a 2½-inch nail can be used, instead of a 1½-inch nail. Two inches of the nail will be angled into the wood. A longer nail means deeper penetration into the wood member.
Another advantage is that this invention makes it easier to nail. By placing the nailing surface at an angle to the intersecting structural members, a contractor can easily swing a hammer, and hit the nail head squarely with the hammer. Most other connectors have the nails near the edge of the structural member, and perpendicular to it making nailing difficult.
Still another advantage of this invention is that it is stronger than prior art connectors because of the double bend at the angled nail, instead of a single bend. This invention lies against both structural members. This invention is simple to manufacture. This invention uses a nail hole with no deformation. This invention has no snagging.
Another advantage is that this invention helps prevent wood structural members from twisting and flexing during strong winds and seismic events, thereby preventing detaching of structural members from each other. It stiffens the connection of two intersecting structural members, helping to transfer lateral or lifting loads throughout the building and into the foundation.
Still another advantage is this invention helps prevent splitting of laminated wood members such as plywood glued laminated timbers (glulam and prefabricated wood joists (microlams). This invention drives nails at an acute or right angle into the layers of the plywood.
During an earthquake or a hurricane, a building with this invention will be a sturdier unit, resisting and transferring destructive forces to the ground.
Many homes were constructed with the best materials and by competent carpenters, but used the time-honored method of connecting slopped and intersecting structural members with toe nails. Toe-nailing drives the nail from near the edge of one structural member into an adjacent structural member. This weak connection is still in use today. Earth tremors and hurricanes always destroy the weakest parts of a house. By making the connections strong, there will be less damage.
It is a further object of this invention that it easily and quickly protects houses from the destructive forces of earthquakes and hurricanes. It is a still further object that the connectors are strong, attractive, permanent, functional, uncomplicated, simple to manufacture, easy to install, and economical. All embodiments can be made from a single sheet metal blank, without welding.
As a retrofit, a handy homeowner can install this invention, or have it installed. The homeowner can easily see that the home is protected instead of wondering if metal connectors were installed correctly during construction, or installed at all. As a retrofit, an insurance agent can observe that the home is protected and give appropriate discounts. Perspective home buyers can perceive that the building is protected, so the seller can ask for a better price.
Since this invention cradles the structural member, and has a wide base anchored to the member, torsional twisting and flexing of the member is significantly reduced over prior art hurricane clips, as is cross-grain splitting. Edges of the connector are slightly rounded for strength, ease of handling, and avoiding stress-fracturing associated with sharp corners.
These and other objectives of the invention are achieved by simple and economical connectors that allow a contractor or home owner to easily secure the weakest parts of a building against earth tremors and high winds. Advantages of each will be discussed in the description. Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.